The present invention relates generally to solar heating methods and more particularly to solar heating methods in which a heat exchanging, fluid medium is heated by circulating the medium through a panel exposed to solar radiation.
In solar heating methods, it is conventional to circulate a heat exchanging, fluid medium through a panel exposed to solar radiation to heat the fluid medium. The fluid medium is then circulated through a heat exchanger to transfer, to a system external to the fluid medium, the heat absorbed by the fluid medium while circulating through the panel. Solar heating methods generally utilize an inclined panel having upper and lower interior surfaces spaced apart to define therebetween one or more inclined channels through which the fluid medium is circulated. An example of such a panel is disclosed in Brackman Defensive Publication No. T952,004, dated Nov. 2, 1976.
Harter, U.S. Pat. No. 4,060,070, discloses a solar heating panel composed of darkened material and having a multiplicity of parallel tubes through which the fluid medium is circulated.
Hastwell, U.S. Pat. No. 4,062,351, discloses a solar heating method in which the fluid medium is circulated through a clear, undarkened panel, but the fluid medium is a dark fluid such as oil. Menardi, U.S. Pat. No. 3,939,819, discloses a solar heating method in which the fluid medium contains a darkening ingredient, such as carbon black particles or a dye.
Ward, U.S. Pat. No. 3,934,323 discloses a solar heating method in which a fluid is circulated through an inclined panel having a multiplicity of parallel channels through which the fluid flows.
The solar heating methods disclosed in the above-noted prior art have problems which interfere with the efficiency of converting solar radiation to usable heat energy or otherwise interfere with the optimum operation of the solar heating panel. For example, particles added to the fluid medium to assist in the absorption of radiant energy often tend to stick to the surface of the panel or to settle out of suspension in the fluid. Bubbles or air spaces can form adjacent the upper interior surface of the panel, and this interferes with the transfer of heat energy from the solar radiation to the fluid medium. The fluid medium can become non-uniformly distributed among the several panel channels. One or more of these or other problems are inherent in the solar heating methods disclosed in the above-noted prior art patents.